| Инд. авторы: | Golovin A.V., Korsakov A.V., Zaitsev A.N. |
| Заглавие: | In situ ambient and high-temperature Raman spectroscopic studies of nyerereite (Na,K)(2)Ca(CO3)(2): can hexagonal zemkorite be stable at earth-surface conditions? |
| Библ. ссылка: | Golovin A.V., Korsakov A.V., Zaitsev A.N. In situ ambient and high-temperature Raman spectroscopic studies of nyerereite (Na,K)(2)Ca(CO3)(2): can hexagonal zemkorite be stable at earth-surface conditions? // Journal of Raman Spectroscopy. - 2015. - Vol.46. - Iss. 10. - P.904-912. - ISSN 0377-0486. - EISSN 1097-4555. |
| Внешние системы: | DOI: 10.1002/jrs.4756; РИНЦ: 24961251; SCOPUS: 2-s2.0-84944150206; WoS: 000363090200012; |
| Реферат: | eng: In this study we present Raman spectroscopy data obtained from a naturally occurring orthorhombic nyerereite (Na,K)(2)Ca(CO3)(2) from the Oldoinyo Lengai volcano (Tanzania) at ambient and high temperature. Nyerereite was heated up to 300 degrees C, 400 degrees C and 500 degrees C, and is believed to have been transformed at high temperatures to hexagonal - and -phases similar to zemkorite, (Na,K)(2)Ca(CO3)(2). There are no major differences in the chemical composition of natural nyerereite and zemkorite. However, Raman spectra reveal significant differences between the nyerereite at ambient temperature and the phases obtained in the course of all our high-temperature experiments. In situ measurements show that none of the high-temperature hexagonal phases are quenchable, even at very high cooling rates (up to 50-80 degrees C/min), and they transform to nyerereite at ambient temperature. Contrary to previous studies even the presence of high K2O (up to 7.5wt.%) did not stabilize the hexagonal structure during cooling. The cooling rates in our experiments were much higher than those at natural magmatic or hydrothermal systems; therefore hexagonal zemkorite is not likely to survive within natural systems as it transforms to nyerereite at ambient conditions. Thus, we do not expect to find zemkorite in any magmatic, metasomatic or hydrothermal rocks exposed at the Earth's surface. Copyright (c) 2015 John Wiley & Sons, Ltd.
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| Ключевые слова: | YAKUTIA; TANZANIA; CARBONATE; MELT INCLUSIONS; UNALTERED KIMBERLITES; OLDOINYO-LENGAI; PETROGENESIS; UDACHNAYA-EAST PIPE; kimberlite and carbonatite; Raman spectroscopy; alkaline carbonates; nyerereite; zemkorite; KIMBERLITE MAGMA EVOLUTION; MANTLE; |
| Издано: | 2015 |
| Физ. характеристика: | с.904-912 |